Problem: If $7a + 4b + 9c = 2$ and $7x + 9y = 2$, what is $63y - 7a - 4b - 9c + 49x$ ?
$= -7a - 4b - 9c + 49x + 63y$ $= (-1) \cdot (7a + 4b + 9c) + (7) \cdot (7x + 9y)$ $= (-1) \cdot (2) + (7) \cdot (2)$ $= -2 + 14$ $= 12$